Former French Open champion Francesca Schiavone knew she was in trouble long before she ever stepped onto the court at Arthur Ashe Stadium.

Last week, after learning her first-round U.S. opponent would be Serena Williams, the No. 1 player in the world, one thought popped into her head.

“Oh, s–t,” Schiavone said.

Last night, Schiavone’s worst fears proved well-founded. The top-seeded Williams looked as dominant as ever, dragging Schiavone through a 60-minute clinic, a 6-0, 6-1 assault of the 33-year-old Italian in front of 21,943 witnesses.

Williams, 31, opened her quest for her second straight Open title — and fifth overall — without recording a single ace, but with powerfully consistent and efficient groundstrokes. She won 24 of 30 first-set points and never faced a break point in the match while producing just eight unforced errors.

Hoping to become the oldest U.S. Open women’s champion of the Open Era, Williams improved to 53-1 in first-round matches at Grand Slams. She will face Galina Voskoboeva in the second round.

“It was my best match of the hardcourt season,” said Williams, whose most recent match ended with a loss to Victoria Azarenka in the finals in Cincinnati. “I think it was best I lost in Cincinnati because it gave me a little push and made me more motivated and not just go through the motions.”

Even in the most comfortable moments of the match, Williams wouldn’t smile — or relent. Even as the score stretched, she attempted to chase down every ball and produced grunts in the final game as loud as any in the first set.

Williams entered the tournament as the player to beat and left the court last night looking as difficult to beat as ever.

“I always say, I think she’s [one] of the best athletes we’ve ever had in the world,” Schiavone said. “We are speaking about some of the best, like Steffi Graf, Billie Jean King, [Martina] Navratilova. We are speaking about something that is really unique. You know that. I don’t have to say that.”